1. Field of Invention
The present invention relates to an adaptive harmonic rejection (HR) receiving device and method, and specifically to an adaptive HR receiving device and method in a broadband communication system.
2. Description of Related Arts
In broad band system, input frequency range could cover several octaves. For example, in cable TV system (DVB-C), input frequency runs from 111 MHz to 862 MHz. Thus the mixer could down-convert input signals around local oscillation (LO) harmonics to the desired band, then cause receiving degradation, and even failure. To avoid this, harmonic rejection (HR) receiver with the certain degree rejection is extensively used in broad band system. Realizations of harmonic rejection receiver (HRR) employ RF (radio frequency) tracking filter and harmonic rejection mixer.
However, the HR receivers have linearity degradation than non-harmonic rejection (NHR) receivers, and even introduce more noise. In previous realization, all the existing manners for harmonic rejection are all passive, that is, within the band needed harmonic rejection, HR mixer is fixed in the receiver chain and it does not have freedom to switch back to non-harmonic rejection receiving chain even when there is weak signal or no signal presenting at LO harmonic frequency. HR mixer is more complex than a simple hard-switching mixer and the complexity of HR mixer is usually paid by NF and linearity degradation.